File:NWA 5717 — Dual Lithologies of Primordial Matter Never Seen Before (50990956998).jpg

<a href="https://www.lpi.usra.edu/meteor/metbull.php?code=49399" rel="noreferrer nofollow">NWA 5717</a> contains primordial matter never before seen and it contains the pristine constituents of the solid planets. It features two lithologies (visibly distance as light and dark) packed with a galaxy of chondrules and other inclusions, along with a rim of fusion crust. This is among the largest complete slices of some of the most primitive planetary materials known.

The vast majority of all meteorites are referred to as ordinary chondrites — stone meteorites that contain silicate-rich spherules known as chondrules. Of the tens of thousands of chondrites, NWA 5717 is one of just 28 that originated from a previously unknown asteroid, never before sampled, and as such are designated as being ungrouped (CH-UNGR).

Moreover, the vast majority of all chondrites are metamorphosed from heating post-aggregation, so having a peek of their original composition is obscured. That is not the case here.

NWA 5717 is also the only meteorite within this select group that features a "3.05 subtype" which makes it among the most primitive planetary materials known. Specifically, unlike 99.9% of all meteorites, the constituents of this meteorite are unchanged since their origins in the early solar nebula. Only six pounds of similarly primitive planetary material was known to exist prior to NWA 5717's discovery.

Unmetamorphosed meteorites like NWA 5717 are the raw ingredients from which our solar system formed. It was the formation of chondrules out of the solar nebular cloud and their subsequent accretion that is largely responsible for the formation of our planets.

“NWA 5717 ungrouped chondrite, one of the most pristine extraterrestrial samples of meteorite available for study.” — <a href="https://originslab.uchicago.edu/content/people" rel="noreferrer nofollow">U of Chicago Origins Lab</a>

The 2010 abstract in the Journal of the Lunar and Planetary Conference was entitled, <a href="https://www.lpi.usra.edu/meetings/lpsc2010/pdf/1280.pdf" rel="noreferrer nofollow">The Extra-Ordinary Chondrite: NWA 5717</a> and features a photo of this slice. NASA JSC <a href="https://ntrs.nasa.gov/api/citations/20170001702/downloads/20170001702.pdf" rel="noreferrer nofollow">studied</a> it in 2017, and there's even a <a href="Even" rel="noreferrer nofollow">book</a> on it!

A <a href="https://reader.elsevier.com/reader/sd/pii/S0012821X18302243" rel="noreferrer nofollow">2018 analysis</a> of chondrule size — sampling 13K particle sizes from NWA5717 and comparing them to Allende, —challenges some details of the current solar system formation hypotheses: "Chondrite classification schemes, astrophysical disk models that predict a narrow chondrule size population and/or a common localized formation event, and conventional particle analysis methods must all be critically reevaluated. We support the idea that distinct “lithologies” in NWA 5717 are nebular aggregates of chondrules. If ≥cm-sized aggregates of chondrules can form it will have implications for planet formation and suggests the sticking stage is where the preferential size physics is operating.

The fact that particle size distributions in both lithologies of NWA 5717 and Allende are very similar in shape after scaling to a common mean size implies the existence of a common, possibly universal, aggregation process. Ultimately, if these size-selective aerodynamic effects allow particle sticking to proceed to larger aggregation sizes than currently expected, the primary formation of planetesimals becomes much easier."